Total costs accrued as of the balance sheet date for environmental loss contingencies.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Commitments and Contingencies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Rent expense	$ 2,500,000	$ 1,900,000	$ 1,800,000
Provision for remediation costs	$ 0
Samedan
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired	100.00%
Comin
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	47.34%
Temin
Business Acquisition [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	44.39%